Ringer's Lactate is NOT a Colloid Solution
Ringer's lactate is a crystalloid solution, not a colloid. Among the options listed, Ringer's lactate is the solution that does not belong in the colloid category, while human albumin, Hemocell (a gelatin-based colloid), and dextran are all true colloid solutions 1.
Understanding the Distinction
Crystalloid vs. Colloid Classification
Ringer's lactate is definitively classified as a balanced crystalloid solution containing sodium (130 mmol/L), potassium (4 mmol/L), chloride (108 mmol/L), calcium (0.9 mmol/L), and lactate (27.6 mmol/L), with an osmolarity of 273-277 mOsm/L 2.
Crystalloids are solutions of small molecules that freely cross capillary membranes and distribute throughout the extracellular space, requiring larger volumes for resuscitation 3.
Colloids contain large molecules (proteins or polysaccharides) that remain primarily in the intravascular space, providing more sustained volume expansion per milliliter infused 3, 4.
The Colloid Solutions Listed
Human albumin is a natural colloid derived from human plasma proteins that provides effective volume expansion but at higher cost 3.
Dextran is a synthetic colloid (polysaccharide) that has been used for volume expansion, though it carries risks of anaphylaxis and potential renal complications 1, 3, 5.
Hemocell (gelatin-based colloid) is a synthetic colloid with limited effectiveness compared to other colloids but fewer adverse effects than dextran 3.
Clinical Implications of This Distinction
Volume Distribution Differences
Crystalloids like Ringer's lactate require approximately 3-4 times the volume of colloids to achieve equivalent intravascular volume expansion because only about 25% remains intravascular after one hour 4.
In one study, only 6% of infused Ringer's lactate remained as plasma volume expansion at 1 hour, compared to 51% of a 3% dextran solution 4.
Current Guideline Recommendations
Balanced crystalloids like Ringer's lactate are now recommended as first-line fluid therapy in most critically ill patients over both 0.9% saline and synthetic colloids, based on improved mortality and renal outcomes 1, 2.
Synthetic colloids have fallen out of favor due to associations with worse neurological outcomes and potential renal toxicity, particularly in patients with subarachnoid hemorrhage 1.
The choice between crystalloid and colloid is less important than ensuring adequate fluid resuscitation, though balanced crystalloids are generally preferred for initial management 3.